Engine exhaust system with water entrapment

ABSTRACT

The present disclosure relates to an exhaust treatment system including a muffler body having a water collection reservoir defined between inner and outer walls of the muffler body. The present disclosure also relates to a vertical muffler having an outlet pipe and a baffle for stabilizing the outlet pipe within the muffler. The baffle includes an integral necked portion that fits within a lower end of the outlet pipe. A water collection region is defined between the necked portion and an inner surface of the outlet pipe.

CROSS REFERENCE TO RELATED APPLICATIONS

This applications claims the benefit of U.S. Provisional Patent Application Ser. No. 60/626,826, filed Nov. 9, 2004 and U.S. Provisional Patent Application Ser. No. 60/655,273, filed Feb. 15, 2005.

TECHNICAL FIELD

The present invention relates generally to engine exhaust treatment devices having cores such as catalytic converters or diesel particulate filters.

BACKGROUND

To reduce air pollution, engine exhaust emissions standards have become increasingly more stringent. Aftertreatment devices have been developed to satisfy these increasingly stringent standards. For example, catalytic converters have been used to reduce the concentration of pollutant gases (e.g., hydrocarbons, carbon monoxide, nitric oxide, etc.) exhausted by engines. U.S. Pat. No. 5,355,973, which is hereby incorporated by reference, discloses an example catalytic converter. With respect to diesel engines, diesel particulate filters have been used to reduce the concentration of particulate matter (e.g., soot) in the exhaust stream. U.S. Pat. No. 4,851,015, which is hereby incorporated by reference, discloses an example diesel particulate filter. Other example types of aftertreatment devices include lean NOx catalyst devices, selective catalytic reduction (SCR) catalyst devices, lean NOx traps, or other device for removing for removing pollutants from engine exhaust streams.

Water from rainfall, road spray, or a vehicle washing cycle can sometimes enter a vehicle exhaust system. Also, under certain conditions, water vapor from the engine exhaust can condense in the muffler and tailpipe. When an aftertreatment device such as a catalytic converter is incorporated into the exhaust system, liquid water can pose certain problems. In particular, exposure of the aftertreatment device to water is not desirable because water has a tendency to adversely affect the catalyst, the substrate (core) on which the catalyst is applied, and the catalyst substrate mounting system. Accordingly, it is desirable to inhibit water from wetting the aftertreatment device.

SUMMARY

Certain aspects of the present disclosure relate to structures for inhibiting liquid water from wetting aftertreatment devices within vehicle exhaust systems.

A variety of other aspects of the invention are set forth in part in the description that follows, and in part will be apparent from the description, or may be learned by practicing the invention. The aspects of the invention relate to individual features as well as combinations of features. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an exhaust system arrangement having features that are examples of inventive aspects in accordance with the principles of the present disclosure;

FIG. 1A is an enlarged detail view of a portion of FIG. 1;

FIG. 1B is an enlarged detail view of another portion of FIG. 1;

FIG. 2 is a left side view of the upper portion of the exhaust system of FIG. 1;

FIG. 3 illustrates an alternative exhaust system arrangement having features that are examples of inventive aspects in accordance with the principles of the present disclosure;

FIG. 3A is an enlarged detailed view of the upper portion of the exhaust system arrangement of FIG. 3;

FIG. 4 is a cross-sectional view of an adapter that can be used in yet another alternative exhaust system arrangement and having features that are examples of inventive aspects in accordance with the principles of the present disclosure;

FIG. 5 is a bottom view of the adapter of FIG. 4; and

FIG. 6 illustrates an alternative exhaust system arrangement having features that are examples of inventive aspects in accordance with the principles of the present disclosure.

While the invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail below. It is to be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the invention is intended to cover all modifications, equivalents, and alternatives falling within the scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION

In the following detailed description, references are made to the accompanying drawings that depict various embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized, and structural and functional changes may be made without departing from the scope of the present invention.

FIG. 1 illustrates an exhaust system arrangement including a vertical muffler 20 and a vertical exhaust stack 22. A diameter reducer 24 is used to couple the lower end of the stack 22 to the upper end of the vertical muffler 20. An aftertreatment device 26 (e.g., a catalytic converter) is mounted within the vertical muffler 20.

The vertical stack 22 has several features adapted to reduce the likelihood for water to enter the stack and travel downwardly to the aftertreatment device 26. For example, as shown in FIG. 1, a mid region of the stack 22 includes a jog 27 having a first offset distance O₁. In one embodiment, the offset distance O₁ is at least equal to the diameter of the stack 22. The jog 27 ensures that water entering the stack and falling downwardly will impinge upon wall 28 of the stack prior to reaching the aftertreatment device 26. When the water impinges on the wall 28, the heat of the stack often causes evaporation. Otherwise, the water runs downwardly along the wall of the stack and is captured as described later in the specification.

To further protect the aftertreatment device 26 from water impingement, a top end 29 of the stack 22 includes additional features for preventing water from entering therein. For example, in one embodiment, the top end 29 of the stack 22 is curved as shown in FIG. 2. The curvature at the top end 29 of the stack 22 provides a second offset distance O₂. In one embodiment, the offset distance O₂ is at least about ⅓ of the diameter of the stack 22. The curvature causes the top end 29 of the stack 22 to be aligned at an angle θ relative to a main vertical portion 31 of the stack 22. Preferably, the angle θ is at least about 45 degrees. The top end 29 of the stack 22 further includes a mitre cut 30 configured to prevent water from entering the stack 22. In one embodiment, the mitre cut 30 is aligned along a vertical plane such that the perimeter edge of the outlet end of the stack is aligned within the vertical plane.

The diameter reducer 24 includes an upper end 40 connected to the stack 22 and a lower end 42 coupled to the vertical muffler 20. In one non-limiting embodiment, the upper end 40 of the diameter reducer 24 is welded to the lower end of the stack 22, and the bottom end 42 of the diameter reducer 24 includes a flange 44 (see FIGS. 1 and 1B) that interfaces with a flange 46 of the muffler 20. Preferably, a clamp such as a v-band clamp is mounted around the flanges 44, 46 to couple the diameter reducer 24 and the muffler 20 together. The diameter reducer 24 also includes a diameter taper 47 having a radius that is generally smooth. Preferably, the radius is sufficiently gradual to prevent water from leaving the surface of the reducer 24 and dripping onto the aftertreatment device.

Referring again to FIG. 1, the muffler 20 includes an outer body 50 having a double wall construction. The outer body 50 includes a cylindrical, main body portion 52 and a tapered end portion 54. The aftertreatment device 26 is mounted within the main body portion 52 of the muffler 20.

The main body portion 52 of the outer body 50 has a double wall configuration including a generally cylindrical outer wall 53 spaced outwardly from a generally cylindrical inner wall 55. An annular insulating space 57 is defined between the walls 53, 55. The space 57 can be filled with air or an insulating material such as fiberglass, ceramic fiber or other materials have effective thermal insulating properties. The aftertreatment device 26 is mounted within the passage defined by the inner wall 55.

The tapered end portion 54 also has a double wall configuration defined by an outer wall 59 spaced outwardly from an inner wall 61. An annular water collection reservoir 63 is defined between the walls 59, 51. The reservoir 63 includes an open top end 65 and a closed bottom end 67. The closed bottom end 67 is located at the interface between the main body portion 52 and the tapered end portion 54. The closed bottom end 67 prevents water from passing from the reservoir 63 into the insulating space 57 of the main body portion 52. In certain embodiments, the outer wall 59 can define one or more drain holes for draining water from the reservoir 63 to the exterior of the muffler body.

The outer wall 59 of the tapered end portion 54 includes a cylindrical lower portion 71, a tapered (e.g., truncated conical) intermediate portion 73 and a cylindrical upper portion 75. The lower portion 71 of the outer wall 59 overlaps and is secured to (e.g., welded) to the outer wall 53 of the main body portion 52. The top end of the upper portion 75 defines the flange 46 of the muffler 20.

The inner wall 61 of the tapered end portion 54 includes a lower end 81 that encloses the bottom of the reservoir 63. The lower end 81 is secured (e.g., welded) to the inner and outer walls 55, 53 of the main body portion 52 at locations 83, 85 (see FIG. 1A). The inner wall 61 also includes a tapered (e.g., truncated conical) intermediate portion 87 that opposes and is generally parallel to the intermediate portion 73 of the outer wall 59. The inner wall 61 further includes a generally cylindrical upper end portion 89. The upper end portion 89 extends in an upright direction and opposes and is generally parallel to the upper portion 75 of the outer wall 59. The upper portions 75, 89 cooperate to define the open top end of the reservoir 63.

In use, water that migrates downwardly within the stack is captured in the water collection reservoir 63 and accumulates in the truncated conical portion of the reservoir. The reservoir prevents water from reaching the aftertreatment device. Preferably, heat from the exhaust evaporates water from within the reservoir before the reservoir overflows. In other embodiments, a drain hole can be provided for draining water from the bottom end of the reservoir.

FIG. 3 illustrates an alternative exhaust system arrangement including a first conduit 122, a second conduit 124, and a third conduit 126. The second conduit 124 is mounted between the first and third conduits 122, 126. An aftertreatment device 128 is mounted within the second conduit 124. Flange interfaces 138 are provided between the first and second conduits 122,124, and between the second and third conduits 124,126. Clamps 144 (e.g., V-band clamps) are provided at the flange interfaces 138 to secure the conduits 122, 124 and 126 together. The flanges assist in mechanically coupling the conduits 122, 124, 126 together, and in sealing the ends of the conduits.

In the depicted embodiment of FIG. 3, the conduits 122, 124, and 126 are part of a muffler unit 121. The conduit 122 forms an inlet section having a flanged end 160 adapted for connection to an inlet pipe, while the conduit 126 forms an outlet section having a flanged end 170 adapted for connection to an outlet pipe. The inlet section includes a diameter expander 161 while the outlet section includes a diameter reducer 171. A diesel oxidation catalyst 162 (i.e., a catalytic converter) is shown mounted within the conduit 122. The aftertreatment device 128 mounted within the conduit 124 is depicted as a diesel particulate filter. The flange interfaces 138 allow the diesel particulate filter to be easily removed for servicing (e.g., cleaning).

The muffler unit 121 has a double-wall construction. For example, conduit 122 includes an inner conduit 122 i surrounded by an outer conduit 122 o. The conduit 124 also has a double-wall construction including an inner conduit 124 i surrounded by an outer conduit 124 o. The conduit 126 further has a double-wall construction including an inner conduit 126 i surrounded by an outer conduit 126 o.

Annular insulating space 123 is defined between the inner and outer walls of the muffler. The insulating space 123 can be filled with only air, or can be filled with an insulating material such as fiberglass, ceramic fiber or other materials having effective thermal insulating properties.

The inner wall 126 i of the conduit 126 includes a lower portion 200, an intermediate portion 202 and an upper portion 204. The lower portion 200 is generally cylindrical and extends in an upright direction. The intermediate portion 202 is tapered (e.g., a truncated cone) and extends radially inwardly from the lower portion 200. The upper portion 204 is generally cylindrical and extends in an upright direction from the intermediate portion 202 to the flanged end 170 of the muffler unit 121.

The outer wall 126 o of the conduit 126 includes a lower portion 206, an intermediate portion 208 and an upper portion 210. The lower portion 206 is generally cylindrical and is generally parallel to the lower portion 200 of the inner wall 126 i. The intermediate portion 208 is tapered (e.g., a truncated cone) and is generally parallel to the intermediate portion 202 of the inner wall 126 i. The upper portion 210 is generally cylindrical and extends in an upright direction from the intermediate portion 208 to the flanged end 170 of the muffler unit 121. The upper portion 210 of the outer wall 126 o is preferably secured (e.g., welded) to the upper portion 204 of the inner wall 126 i.

As shown at FIG. 3A, the flanged end 170 is defined by member 191 that is secured to the outer wall 126 o. The member 191 also includes a generally cylindrical portion 173 that extends downwardly from the flanged end 170. A lower end 175 of the cylindrical portion 173 is secured (e.g., welded) to the exterior of the outer wall 126 o. An annular water capturing space 177 is defined between the cylindrical portion 173 and the wall 126 o. A top end 179 of the space 177 is open, while a bottom end 181 of the space 177 is closed by the wall 126 o. The cylindrical portion 173 defines one or more drain holes 183 for draining water from the space 177.

As described above, the aftertreatment device 26 is identified as a catalytic converter. However, it will be appreciated that structures in accordance with the principles of the present disclosure can be used to inhibit water from wetting a variety of different types of aftertreatment devices. Example aftertreatment devices include catalytic converters, diesel particulate filters, lean NOx catalyst devices, selective catalytic reduction (SCR) catalyst devices, lean NOx traps, or other devices for removing pollutants from the exhaust stream.

Catalytic converters, also known as Diesel Oxidation Catalysts or DOC's, are commonly used to convert carbon monoxides and hydrocarbons in the exhaust stream into carbon dioxide and water. Diesel particulate filters are used to remove particulate matter (e.g., carbon based particulate matter such as soot) from an exhaust stream. Lean NOx catalysts are catalysts capable of converting NOx to nitrogen and oxygen in an oxygen rich environment with the assistance of low levels of hydrocarbons. For diesel engines, hydrocarbon emissions are too low to provide adequate NOx conversion, thus hydrocarbons are required to be injected into the exhaust stream upstream of the lean NOx catalysts. SCR's are also capable of converting NOx to nitrogen and oxygen. However, in contrast to using hydrocarbons for conversion, SCR's use reductants such as urea or ammonia that are injected into the exhaust stream upstream of the SCR's. NOx traps use a material such as barium oxide to absorb NOx during lean bum operating conditions. During fuel rich operations, the NOx is desorbed and converted to nitrogen and oxygen by catalysts (e.g., precious metals) within the traps.

Diesel particulate filter substrates can have a variety of known configurations. An exemplary configuration includes a monolith ceramic substrate having a “honey-comb” configuration of plugged passages as described in U.S. Pat. No. 4,851,015 that is hereby incorporated by reference in its entirety. Wire mesh configurations can also be used. In certain embodiments, the substrate can include a catalyst. Exemplary catalysts include precious metals such as platinum, palladium and rhodium, and other types of components such as base metals or zeolites.

For certain embodiments, diesel particulate filters can have a particulate mass reduction efficiency greater than 75%. In other embodiments, diesel particulate filters can have a particulate mass reduction efficiency greater than 85%. In still other embodiments, diesel particulate filters can have a particulate mass reduction efficiency equal to or greater than 90%. For purposes of this specification, the particulate mass reduction efficiency is determined by subtracting the particulate mass that enters the filter from the particulate mass that exits the filter, and by dividing the difference by the particulate mass that enters the filter.

Catalytic converter substrates can also have a variety of known configurations. Exemplary configurations include substrates defining channels that extend completely therethrough. Exemplary catalytic converter configurations having both corrugated metal and porous ceramic substrates/cores are described in U.S. Pat. No. 5,355,973, that is hereby incorporated by reference in its entirety. The substrates preferably include a catalyst. For example, the substrate can be made of a catalyst, impregnated with a catalyst or coated with a catalyst. Exemplary catalysts include precious metals such as platinum, palladium and rhodium, and other types of components such as base metals or zeolites.

In one non-limiting embodiment, a catalytic converter can have a cell density of at least 200 cells per square inch, or in the range of 200-400 cells per square inch. A preferred catalyst for a catalytic converter is platinum with a loading level greater than 30 grams/cubic foot of substrate. In other embodiments the precious metal loading level is in the range of 30-100 grams/cubic foot of substrate. In certain embodiments, the catalytic converter can be sized such that in use, the catalytic converter has a space velocity (volumetric flow rate through the DOC/volume of DOC) less than 150,000/hour or in the range of 50,000-150,000/hour.

In the depicted embodiments, V-band clamps are used to hold the components together. It will be appreciated that in other embodiments, any number of different types of pipe clamps or fasteners could be used to fasten the parts together. Also, the various aspects of the present disclosure are also applicable to exhaust components (e.g., mufflers) that are not adapted to be readily disassembled.

Referring now to FIGS. 4 and 5, another alternative embodiment of a device used to inhibit water from wetting aftertreatment devices within vehicle exhaust systems is illustrated. The alternative embodiment includes an adapter 300 that mounts between a vertical stack and a muffler component containing an aftertreatment device. In one embodiment, the adapter 300 can be used as an outlet section for a catalytic converter muffler in much the same way as the outlet section provided by conduit 126 of FIG. 3. The aftertreatment device can include, for example, a catalytic converter or a diesel particulate filter.

The adapter 300 includes a housing 302 and a cap 304. A conduit 306 extends through the housing 302. A first end 308 of the conduit 306 is configured to interconnect to a pipe/conduit such as a muffler stack and a second end 310 of the conduit 306 is interconnected to the cap 304. The cap 304 is configured to mount or interconnect to another exhaust system component such as a muffler section containing an aftertreatment device.

The adapter 300 in the illustrated embodiment further includes a water entrapment ring or piece 312 positioned within the conduit 306. The water entrapment piece 312 has a ring shape that defines an open central region 328 (FIG. 5). The water entrapment piece 312 provides a seal 314 between the water entrapment piece 312 and an interior surface 316 of the conduit 306. A first annular reservoir or water capturing space 318 is defined between a shaped region 320 of the water entrapment piece 312 and the interior surface 316 of the conduit 306. When water enters the conduit 306 of the adapter 300 (typically running down the interior surface 316 of the conduit), the water is captured or collected within the first annular reservoir 318 defined by the water entrapment piece 312. The water entrapment piece 312 is constructed to permit exhaust to pass through the open central region 328, yet capture water within the first annular reservoir 318.

A second annular reservoir 322 is located between an exterior 324 of the conduit 306 and the housing 302. The second reservoir 322 has a bottom 326 defined by the cap 304. An aperture or hole 329 formed in the conduit 306 provides fluid communication between the first reservoir 318 and the second reservoir 322. In use, the water entrapment piece 312 captures water within the first reservoir 318. The collected water then drains through the hole 329 in the conduit and into the second reservoir 322. During operation of the aftertreatment device, the cap 304 becomes hot. Any water that has collected within the second reservoir 322 thereby heats and evaporates within the second reservoir 322. The adapter 300 shown in FIGS. 4 and 5 eliminates water drainage along exterior surfaces of the vehicle exhaust system by evaporating the water within the second reservoir. However, in other embodiments, a drain hole may be provided through the outer wall of the adapter 300 for draining water that collects at the second reservoir 322.

Referring now to FIG. 6, another alternative embodiment of a device used to inhibit water from wetting aftertreatment devices within vehicle exhaust systems is illustrated. The muffler 400 includes a lower inlet pipe 402 and an upper outlet pipe 404. A catalytic converter and diesel particulate filter 408 are mounted within the muffler body between the inlet pipe 402 and the outlet pipe or tube 404. The outlet pipe 404 includes an upper end 410 adapted for connection to an exhaust conduit such as a tail pipe, and a lower end 412. The lower end 412 is supported by an annular baffle 414. The baffle 414 includes a central, upwardly necked portion 416 that defines a central exhaust flow opening 418. The upwardly necked portion 416 is fit within the inside of the lower end 412 of the outlet tube 404. The upper edge 420 of the upwardly necked portion 416 is angled inwardly such that a first water collection reservoir 422 is defined between the necked portion 416 and the interior surface 424 of the outlet tube 404. Slots 426 are provided at the lower end 412 of the outlet tube 404 to allow water collected in the collection reservoir 422 to drain out of the first water collection reservoir 422 through the slots 426. The baffle 414 also includes a main body 427 having a top surface 428 that extends radially outwardly from the necked portion 416. The top surface 428 is angled downwardly relative to the lower end 412 of the outlet pipe 404. A lip 430 is provided at the outer edge 432 of the surface 428. The lip 430 defines a second water collection reservoir 434 (e.g., an annular trough or channel) that functions to collect water that drains through the slots 426 and runs downwardly along the surface 428 to lip 430. A drain hole 436 can be provided through the outer wall 438 of the muffler to drain water from the second water collection reservoir 434. The lip 430 also functions as a spacer for spacing an inner body 440 of the muffler 400 from the outer wall 438 of the muffler 400. The spacer functions to stabilize the inner body 440 relative to the outer body 442 and to center the inner body 440 within the outer body 442. The inner body 440 can be secured (e.g., welded) to the baffle 414 adjacent an inner portion of the outer lip 430 of the baffle 414. The outer body 442 can be secured (e.g., welded) to the baffle 414 adjacent an outer portion of the outer lip 430. In the depicted embodiment of FIG. 6, the baffle 414 has a one-piece construction in which the necked portion 416 and the lip 430 are integral with the main body 427. The term “integral” means directly connected by a unitary connection without any intermediate seams on joints.

The configuration provides a number of advantages. For example, the configuration of the baffle 414 with the relatively large necked opening 418 inset within the outlet tube 404 helps to minimize back pressure. Back pressure is also minimized because the baffle 414 and the inner body 440 cooperate to direct flow from the diesel particulate filter 408 to the outlet tube 404 in a relatively smooth manner. The baffle 414 also provides a water collection function at two places. First, water is collected at the inner surface 424 of the outlet tube 404. Second, water is collected at the inner surface 444 of the outer muffler body 442. The baffle 414 also provides the function of directing the flow of water from the first collection area 422 to the second collection area 434. The baffle 414 further functions to stabilize the inner body 440 relative to the outer muffler body 442, and to stabilize the lower end 412 of the outlet tube 404 relative to the inner and outer muffler bodies 440, 442.

The above specification and examples provide a complete description of the manufacture and use of the invention. Since many embodiments of the invention can be made without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended. 

1. A muffler comprising: a muffler body including an outlet having an outlet flange; an aftertreatment device mounted within the muffler body; and the muffler body including inner and outer walls defining an annular water capturing space located adjacent the outlet flange.
 2. The muffler of claim 1, wherein the inner wall bends outwardly to close a lower end of the annular water capturing space.
 3. The muffler of claim 2, wherein the outer wall defines a drain hole for draining water that collects within the annular water capturing space.
 4. An exhaust system comprising: a muffler body including an outlet having an outlet flange; an aftertreatment device mounted within the muffler body; the muffler body including inner and outer walls defining an annular water capturing space located adjacent the outlet flange; and a stack mounted to the outlet flange.
 5. The exhaust system of claim 4, wherein the stack includes a diameter reduced positioned above the water collecting space.
 6. The exhaust system of claim 4, wherein the stack includes a jog providing a stack offset distance equal to at least about one diameter of the stack.
 7. The exhaust system of claim 4, wherein a top end of the stack is curved at least one third a diameter of the stack.
 8. The exhaust system of claim 4, wherein a top end of the stack includes a mitre cut.
 9. A muffler comprising: a muffler body having an inlet and an outlet; an outlet pipe positioned at the outlet of the muffler body, the outlet pipe including an upper end and a lower end; an aftertreatment device mounted within the muffler body beneath the lower end of the outlet pipe; and a baffle for stabilizing the lower end of the outlet pipe within the muffler body, the baffle including an integral inwardly necked portion that fits into the lower end of the outlet pipe, the inwardly necked portion defining an interior exhaust flow opening positioned within the outlet pipe, the inwardly necked portion also defining an annular water collection region positioned between the necked portion and an inner surface of the outlet pipe.
 10. The muffler of claim 9, wherein the baffle includes an annular main body that extends outwardly and downwardly from the lower end of the outlet pipe.
 11. The muffler according to claim 9, wherein the lower end of the outlet pipe defines a drain opening that allows water to drain from the water collection region to a location outside the outlet pipe.
 12. The muffler according to claim 11, wherein the drain opening is defined by a slot at the lower end of the outlet pipe.
 13. The muffler according to claim 12, wherein a plurality of slots are defined at the lower end of the outlet pipe.
 14. The muffler according to claim 9, wherein the muffler body includes an inner wall and an outer wall, and wherein the baffle includes an outer lip that spaces the inner wall from the outer wall.
 15. The muffler according to claim 14, wherein water from the water collection region drains outwardly along a top side of the baffle and collects at an annular water collection channel defined by the outer lip of the baffle, the annular water collection channel being positioned between the inner and outer walls of the muffler body.
 16. A muffler comprising: a muffler body having an inlet and an outlet, the muffler body including an inner wall and an outer wall; an outlet pipe positioned at the outlet of the muffler body, the outlet pipe including an upper end and a lower end; an aftertreatment device mounted within the muffler body beneath the lower end of the outlet pipe; and a one-piece baffle for stabilizing the lower end of the outlet pipe within the muffler body, the baffle including an inwardly necked portion that fits into the lower end of the outlet pipe, the inwardly necked portion defining an interior exhaust flow opening positioned within the outlet pipe, the inwardly necked portion also defining an annular water collection region positioned between the necked portion and an inner surface of the outlet pipe, the baffle also including an outer spacer portion that fits between the inner and outer walls of the muffler body.
 17. The muffler of claim 16, wherein the spacer defines an annular water collection channel positioned between the inner and outer walls.
 18. The muffler of claim 16, wherein the baffle includes an annular main body that extends outwardly and downwardly from the upwardly necked portion to the outer spacer portion.
 19. The muffler of claim 18, wherein the lower end of the outlet pipe defines a drain opening that allows water to drain from the water collection region to a top surface of the annular main body of the baffle.
 20. The muffler of claim 19, wherein the outer spacer portion defines an outer water collection channel for collecting water that runs down the top surface of the annular main body of the baffle. 